In integrated circuits (ICs), the internal circuitry which provides the functionality of the IC is coupled to the leads of a chip package through the use of bonding pads. In many instances, the bonding pads have associated circuitry coupled thereto to transfer the signal present on the bonding pad to the internal circuitry. In the IC industry, a bonding option is frequently used to provide a family of devices (a number of different devices) using a single die.
In a standard Complementary Metal Oxide Semiconductor (CMOS) design, the bonding option is commonly achieved by connecting a bonding pad to an adjacent V.sub.cc (or V.sub.ss) pad with a bonding wire. Since the bonding pad is usually connected to the gate of an input buffer, it has to be pulled to V.sub.ss (or V.sub.cc)through a resistor or a transistor in silicon in a default configuration.
In the default configuration, a bonding pad is generally tied to V.sub.ss through a transistor thereby providing a logical zero signal to the internal circuitry. In an alternate configuration (bonding option), the bonding pad is bonded to a neighboring V.sub.cc pad, thereby providing a logical high signal to the internal circuitry. By using the bonding option approach, a single IC design can perform multiple functions. If the bonding pad is connected to V.sub.ss, a logic zero is passed to the internal circuitry resulting in the internal circuitry performing a first function. If the bonding pad is connected to V.sub.cc, a logic one is passed to the internal circuitry resulting in the internal circuitry performing a second, or alternate, function. Every bonding pad connected to the IC structure can be bonded in the fashion described above. Thus, through the use of a bonding option, a family of devices using a single die can be provided.
A Problem with the bonding option approach discussed above is that a leakage current flowing from V.sub.cc through the bonding wire and the transistor connected to the bonding pad to ground is present. The amount of leakage current is dependent upon the size of the transistor and process variations. In most applications, the leakage current is in the range of several hundred microamps. In devices such as pacemakers, laptop computers and Personal Digital Assistants (PDA's) which run on battery power, a constant leakage current of such magnitude may cause the device to malfunction or at a minimum reduce battery life.